VIDEO STARTS OUT ONE-WAY - Only the video of the person initiating "Instant Video" is shown. The recipient sees the video of the sender, but their video connection is NOT enabled. Now, the recipient can start sending video, but they don't have to.

AUDIO IS OFF INITIALLY - When the sender starts their video, the recipient receives the video without any sound. They can easily start getting sound by tapping on the speaker icon on the video, but this is great because often you are having a text conversation precisely because you don't want to use audio.

YOU CAN STILL SEE THE CHAT - The video overlays the upper right corner of the chat window, but that's it. You can still see the chat messages and continue having your chat.

This last point is quite important and useful. This "Instant Video" lets you add video to a chat, while still allowing chat to be the primary communication medium.

Regardless, I immediately saw a personal use case. Occasionally I will go to a local coffee shop to pick up muffins for my wife and I. The flavors are always changing. If I don't see one I think she'll like, I often wind up calling - or texting her with the flavors. But it would be actually a bit easier and faster if I texted her "which one do you want?" and then sent her a live video stream where I panned back and forth across the choices. Sure, that may seem a silly use case... but it immediately sprang to my mind.

For "Instant Video" to work, a couple of conditions need to be true:

YOU BOTH NEED THE LATEST MESSENGER APP - You need to have the latest version for either iOS or Android.

YOU BOTH NEED TO BE *IN* THE CHAT - This is key. You can't just open up Messenger and start sending video to someone who is listed in your contacts. You need to actually be in communication with the other person.

Once this second item is true the video icon on the top of the screen starts pulsating - at which point you can start sending "Instant Video".

I'd note that this is the same icon used to initiate a "regular" video call. However, when you are in a chat with someone else the pulsating icon means you can do this new "Instant Video" style of chat.

I found I really liked the overlay aspect. Here's the view I saw on my end:

It worked very well to continue the text conversation while having the video right there, too.

It's an interesting addition as Facebook continues to try to make Messenger be THE tool that people use for messaging. Facebook has this advantage of having an absolutely massive "directory" of users (see "the Directory Dilemma") and so we may see this helping with keep people inside of Facebook's shiny walls.